An object, such as a can or bottle, that is returned to a reverse vending machine (RVM) is usually provided with different marks or patterns that should be analyzed or recognized by the RVM. Such marks can be bar codes, article numbers, particular deposit marks, etc. Different patterns can have different sizes, or require different resolutions to be detected by e.g. a camera. For instance, a finer pattern requires high resolution, while a coarser pattern can be properly detected even with lower resolution. Also, the distance between the object and the camera may be unknown, albeit the distance is typically within a given interval. Hence, the camera's depth of field should generally cover said interval in which the object may appear.
Unrelated to RVMs, U.S. Pat. No. 7,119,842 (Soe) discloses a diaphragm which is mounted in a photographing optical system and which forms a first area and a second area. The first area transmits light rays of the infrared and visible rays spectrum. The second area selectively transmits either of light rays of the infrared or visible rays spectrum. The second area is partly defined by an iris stop. When the second area transmits infrared, the first and second areas together determine the amount of infrared rays reaching a three-dimensional image-capturing CCD. For the visible rays of incident light, the first area determines the amount of rays reaching a two-dimensional image-capturing CCD. With the construction in U.S. Pat. No. 7,119,842, a two-dimensional image of the visible rays and a three-dimensional image of the infrared rays are captured simultaneously through a single photographing lens system, but stop numbers for the visible rays and the infrared rays can be set individually so that both exposure for the two-dimensional image-capturing CCD and exposure for the three-dimensional image-capturing CCD can be set appropriately and simultaneously. Accordingly, images formed out of distinct spectrums are captured simultaneously through a single photographing optical system at appropriate exposure.
Further, U.S. Pat. No. 5,279,397 (Barkan et al.) relates to a multi-resolution bar code reader. U.S. Pat. No. 5,279,397 supposedly facilitate operation of a bar code reader over a wider range of working angles and for a wider range of bar code densities by detecting optically encoded information using two effective sensing spots of different diameter. In one embodiment, two emitters and two detectors are used to provide two different channels optically. In another embodiment, two emitters and one detector are used. The output of the detector is multiplexed in synchronism with pulsing of the individual emitters to produce two channels. The emitters and/or the associated optics differ to provide the two different effective sensing spots and two different resolutions. In yet another embodiment, there is one light emitting element and two photodetectors, and the photodetectors comprise a central circular active area D1 and a surrounding active area D2. D1 produces an analogue signal which represents the average of reflected light received over the small active area D1. Further, analog signals from D1 and D2 are summed to approximate a signal which a larger photodiode would produce. This embodiment hence requires a rather complicated photodetector and related circuitry and processing.